The invention described concerns a communications system for mobile telecommunications and a set of procedures for operating the system.
Up to now no technology is being used by any of the known mobile telecommunications systems which operate for example in the GSM mode (Global System for Mobile Communications) for finding the exact location of a mobile telephone or any other user unit. This means that a subscriber to whom a subscriber number is allocated can be permanently reached within the total area served by the corresponding switching unit, the so called provider.
Hence, when the total area in question covers several adjacent countries and requires a large number of cells for transmitting the information, high charges must be made for each chargeable tariff unit as the charge made for the communications between mobile user units is independent of the distance between the subscribers. In addition, within a GSM mobile communications system, only approximate information concerning the location of a subscriber can be made available. This information is on the whole determined by the inherent organisation of the switching unit. In the inactive mode, i.e. when the subscriber is not carrying out a conversation or the mobile user unit is sending no updating information, the mobile communications network can only ascertain in which area the customer was last located—the area predetermined by the switching unit. And this area predetermined by the switching unit is usually extremely large, i.e. with a diameter of from several kilometers to 100 km, and covers often the geographical area of several area codes and often is subject to changes as a result of dynamic mobile communications network planning. A location which is changing as a result of the subscriber's movements and hence those of his mobile user unit can as a result of the parameters used up to now simply be used in the active mode, i.e. during a conversation, to locate the user units. Because of their method of operation the communications systems used up to now, however, are not suitable for determining in the inactive mode the position of the user units and hence indicating to the subscriber his current position.